A non-EU airline cancels the flight to EU. The passenger accepts alternative rebooking. Now the passenger wants an EU airline to both pay the compensation and to refund the ticket that the passenger agreed to. I think I have more chances of clearning an upgrade request on F0A0 flight than you having a positive outcome with your claim.
Code-share for 261/2004 does not matter, what matters is who operates the flight. In your case it was an AC-operated flight. Also, to document the earliest rebooking opportunity you don't need to (re)-issue the ticket. A simple PNR note suffices. Accepting rebooking means accepting new itinerary.